Electric car air-conditioning apparatus

Abstract: An electric car air-conditioning apparatus, which is small in size and capable of preventing abnormal heating upon occurrence of a failure and preventing damage when a capacitor (11) is connected with its polarity reversed, provided with a current-conduction detecting device (9) for detecting the operation of current conduction of a current conducting device (8) for charging the capacitor (11) with a current from a battery (2), and a power breaking device (4) for breaking a current from the battery (2), wherein a control section (6) actuates the power breaking device (4) to break the current from the battery (2) in the case where the current-conduction detecting device (9) detects the operation of current conduction for a period longer than a predetermined time when the control section (6) is not outputting a control signal for closing a switching device (3) through which power is supplied from the battery (2) to drive a motor-driven air compressor (5), and in the case where the current-conduction detecting device (9) detects the operation of current conduction when the control section (6) is outputting the control signal for closing the switching device (3).

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an electric car air-conditioning apparatus having a motor-driven air compressor driven by the power supplied from a battery. DESCRIPTION OF THE RELATED ART The operation of a conventional electric car air-conditioning apparatus will be described with reference to a circuit diagram of a conventional electric car air-conditioning apparatus shown in Fig. 2. When a battery 2 is connected, a capacitor 11 is charged with a time constant determined by a product of the resistance value of a resistor 8 and the electrostatic capacity value of the capacitor 11. If an input voltage detecting means 7 of a motor-driven air compressor driving unit 1 detects a voltage larger than a predetermined value, a switching device 3 is closed by a control section 6 so that power is supplied from the battery 2 through the switching device 3, so that the air-conditioning motor-driven air compressor 5 is driven by the motor-driven air compressor driving unit 1. The resistance value of the resistor 8 must be large enough to restrain a charging rush current in order to prevent a fuse 10 from breaking. On the other hand, the resistance value must be small enough so that the fuse 10 is broken upon occurrence of a failure such as damage of the motor-driven air compressor driving unit 1 or short-circuiting of the capacitor 11 or the like. Since the fuse 10 must not be broken in a normal operation current, the value of the fuse 10 is set to about 10A. Accordingly, in order to flow a current about 40A to break the fuse 10 surely upon occurrence of a failure, the resistance value of the resistor 8 is set to 7.5 ohm when the voltage of the battery 2 is 300V. In the above-mentioned circuit, in the case where the fuse 10 does not break at the time of a half-failure of the motor-driven air compressor driving unit 1 or the capacitor 11 or the like, that is, for example, in the case where a current of 9A flows, the resistor 8 consumes a large power of (9A) 2 x 7.5ohm = 607.5W. Accordingly, overheating causes deterioration of reliability such as smoking, solder dissolving, wiring damage, and so on. It is therefore necessary to provide a radiator or the like as a countermeasure to overheating. Accordingly the air-conditioning apparatus becomes large in size. When the input voltage to the motor-driven air compressor driving unit 1 does not rise in the case where the capacitor 11 is connected with its polarity reversed, the input voltage detecting means 7 does not detect the fact that the input voltage has exceeded a predetermined value, so that the control section 6 does not close the switching device 3 and the resistor 8 continues to flow a current into the capacitor 11. On the other hand, even in the case where the capacitor 11 is connected with its polarity reversed directly to the battery 2 and the input voltage to the motor-driven air compressor driving unit 1 rises, the input voltage detecting means 7 detects the fact that the input voltage has exceeded the predetermined value and the control section 6 closes the switching device 3. Accordingly, a current continues to flow. As a result, the capacitor 11 is broken, and matters blown out of the capacitor 11 pollutes the air-conditioning apparatus to lower the performance and reliability of the apparatus. The capacitor 11 is a large-size one which has a rated voltage of about 300V and an electrostatic capacity of about 1000µF. Accordingly, the failure of the capacitor 11 has a large influence. Further, if a failure occurs in the switching device 3 or a driving circuit of the switching device 3, the air-conditioning motor-driven air compressor 5 is driven by the motor-driven air compressor driving unit 1 with the switching device 3 kept not-closed. In this case, the current of the motor-driven air compressor 5 flows into the resistor 8. Accordingly there occurs a situation similar to the above-mentioned situation where the fuse 10 does not break. DE 42 26 781 A1 discloses a heat carrier circuit for an electric vehicle. Said heat carrier circuit serves for cooling of the electric motor of the vehicle as well as of the vehicle battery. The waste heat may be used for heating the coupé of the vehicle. DE 33 08 320 A1 describes a circuit for limiting a starting current for use in connection with an electric power supply including a resistance. Said circuit uses a diode, wherein when reaching a predetermined voltage, a relais is activated bridging said resistance and said diode. It is an object of the present invention to provide an electric car air-conditioning apparatus which is small in size, which is capable of preventing abnormal heating upon occurrence of a failure, and which is capable of preventing damage of a capacitor even when the capacitor is connected with its polarity reversed. According to the invention, the above object is achieved by an apparatus according to claim 1. Preferred embodiments are claimed in claims 2 and 3. In other words, in the electric car air-conditioning apparatus according to the present invention, a control section actuates the power breaking device to break the current from the battery in the case where the current-conduction detecting device detects the operation of current conduction for a period longer than a predetermined time when the control section is not outputting a control signal for closing the switching device through which power is supplied from the battery to drive a motor-driven air compressor, and in the case where the current-conduction detecting device detects the operation of current conduction when the control section is outputting the control signal for closing the switching device. In the period in which the control section is not outputting a control signal for closing the switching device, the current conducting device is charging the capacitor with a current supplied from the battery. At this time, the current-conduction detecting device detects the operation of current conduction of the current conducting device. This current conduction is performed for a predetermined time which is necessary for charging. However, there is a possibility that this current conduction continues beyond the predetermined time. This is a case where a half-failure occurs in the motor-driven air compressor driving unit or the capacitor or the like so that a fuse is not broken and a current is left to flow continuously, or a case where the capacitor is connected with its voltage polarity reversed so that a current is left flowing or the like. In such a case where the current conduction continues beyond the predetermined time, the control section actuates the power breaking device to break a current from the battery. Accordingly, there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, and so on, caused by overheating of the current conducting device due to the half-failure of the motor-driven air compressor driving unit or the capacitor or the like. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, and it is therefore possible to prevent the air-conditioning apparatus from becoming large in size. In addition, there is no case where the capacitor is broken due to connection of the capacitor with its polarity reversed. Accordingly, there is no case where matters blown out of the broken capacitor pollute the air-conditioning apparatus to thereby deteriorate the performance and reliability of the apparatus. Accordingly, it is possible to realize an electric car air-conditioning apparatus which is small in size, in which abnormal heating can be prevented from occurring upon occurrence of a failure, and in which damage can be prevented from occurring when the capacitor is connected with its polarity reversed. When the control section is outputting a control signal to close the switching device, the switching device should be closed so that no current flows into the current conducting device because the switching device is connected in parallel to the current conducting device. In this case, however, there is a possibility that the current-conduction detecting device detects the operation of current conduction. That is the case where a failure occurs in the switching device or in a driving circuit of the switching device. The control section detects only the fact that an input voltage exceeds a predetermined value by means of the input voltage detecting means so that the control section outputs a control signal for closing the switching device to thereby make the motor-driven air compressor driving unit drive the air-conditioning motor-driven air compressor. Therefore, the motor-driven air-compressor is driven by the motor-driven air compressor driving unit in the condition where the switching device is not closed. When the current-conduction detecting device detects the operation of current conduction, the control section actuates the power breaking device to break a current from the battery. Accordingly, if a failure is caused in the switching device or the driving circuit of the switching device, there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, or the like, caused by overheating of the current conducting device caused by the fact that the motor-driven air compressor is driven as the switching device is left not-closed so that the current of the motor-driven air compressor flows into the current conducting device. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, so that the air-conditioning apparatus does not become large in size. Accordingly, it is possible to realize an electric car air-conditioning apparatus which is small in size, and in which abnormal heating can be prevented from occurring upon occurrence of a failure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram illustrating an electric car air-conditioning apparatus according to a first embodiment of the present invention; and an electric car air-conditioning apparatus according to a second embodiment of the present invention; Fig. 2 is a circuit diagram illustrating a conventional electric car air-conditioning apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a circuit diagram of an electric car air-conditioning apparatus according to the present invention. This embodiment is different from the conventional electric car air-conditioning apparatus shown in Fig. 2 in a point that a current-conduction detecting device 9 is connected in parallel to a resistor 8, and the output of the current-conduction detecting device 9 is connected to a control section 6. In addition, a power breaking device 4 is connected in series to a battery 2 and a fuse 10, and the input of the power breaking device 4 is connected to the control section 6. The operation of the circuit will be described. In the case of normal operation, if the battery 2 is connected, a capacitor 11 is charged with a time constant depending on the product of the resistance value of the resistor 8 and the electrostatic capacity value of the capacitor 11. Then, if an input voltage detecting means 7 of a motor-driven air compressor driving unit 1 detects a voltage larger than a predetermined value, a switching device 3 is closed by the control section 6. Accordingly, supplied with power through the switching device 3 from the battery 2, the motor-driven air compressor driving unit 1 drives an air-conditioning motor-driven air compressor 5. Assume now that the voltage of the battery 2 is set to 300V, the rated value of the fuse 10 is set to 10A, the resistance value of the resistor 8 is set to 7.5ohm, and the electrostatic capacity of the capacitor 11 is set to 1,000µF. In addition, assume that the predetermined value of the voltage detected by the input voltage detecting means 7 is set to 259V (86.5%) which is a voltage value reached after 15ms, the time twice as long as the time constant 7.5ms. Because of scattering or the like of the time constant or the voltage of the battery 2, in spite of the normal state of the operation, in some cases the power breaking device 4 operates before the input voltage detecting means 7 detects a voltage not lower than the predetermined value. In order to prevent such a maloperation of the power breaking device 4, a predetermined time period concerning the current conduction of the resistor 8 and detected by the current-conduction detecting device 9 is set to 30ms which is four times as long as the time constant 7.5ms. Assume now that a half-failure occurs in the motor-driven air compressor driving unit 1 and the resistance value of the motor-driven air compressor driving unit 1 is 25.8ohm when the control section 6 is not outputting a control signal for closing the switching device 3, that is, when the capacitor 11 is being charged. At this time, a current of: 300V ÷ (7.5ohm + 25.8ohm) = 9A flows into the resistor 8. The power consumption of the resistor 8 becomes: (9A) 2 × 7.5ohm = 607.5W The input voltage of the motor-driven air compressor driving unit 1 becomes: 300V - 7.5ohm × 9A = 232.5V. Therefore, a current flowing in the resistor 8 is 9A which is smaller than the rated value 10A of the fuse 10, so that the fuse 10 does not break. In addition, the input voltage of the motor-driven air compressor driving unit 1 is lower than the predetermined voltage 259V detected by the input voltage detecting means 7. Accordingly, the control section 6 does not close the switching device 3, so that the current of 9A continues to flow in the resistor 8. The voltage 67.5V = 7.5ohm × 9A continues to be produced across the opposite ends of the resistor 8. Accordingly, in the current-conduction detecting device 9 constituted by a series connection of a resistor and a photocoupler, the voltage 67.5V is applied across the opposite ends of the series connection, so that the LED of the photocoupler is lighted and a photo-transistor of an output section is turned on. Accordingly, the control section 6 decide that the resistor 8 is brought into a state of current-conduction, and counts the time of the current-conduction. If the time exceeds the predetermined time of 30ms, the control section 6 actuates the power breaking device 4 so that the power breaking device 4 operates to stop the current applied to the resistor 8. Also in the case where the capacitor 11 has a half-failure, or is connected with its polarity reversed, a current continues to flow into the resistor 8 and the power breaking device 4 operates in the same manner as mentioned above. Therefore, there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, and so on, caused by overheating of the resistor 8 due to the half-failure of the motor-driven air compressor driving unit 1 or the capacitor 11 or the like. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, so that it is possible to prevent the air-conditioning apparatus from becoming large in size. In addition, there is no case where the capacitor 11 is broken due to the fact that the capacitor 11 is connected with its polarity reversed. Accordingly, there is no case where matters blown out of the broken capacitor 11 pollute the air-conditioning apparatus to thereby deteriorate the performance and reliability. Assume now that a failure occurs in the switching device 3 when the control 6 is outputting a control signal to close the switching device 3, that is, when the input voltage detecting means 7 of the motor-driven air compressor driving unit 1 detects a voltage larger than a predetermined value so that the motor-driven air compressor driving unit drives the air-conditioning motor-driven air compressor 5. At this time, a current of several amperes is made to flow into the resistor 8 by the motor-driven air compressor 5, a voltage is generated across the opposite ends of the resistor 8 and the current-conduction detecting device 9 operates in the same manner as mentioned above. Then, the control section 6 decides that the resistor 8 is brought into a state of current conduction, and actuates the power breaking device 4 immediately so that the power breaking device 4 operates to stop the current applied to the resistor 8. Also in the case where a failure occurs in the driving circuit of the switching device 3, the power breaking device 4 operates in the same manner. Accordingly, in the case where a failure occurs in the switching device 3 or the driving circuit of the switching device 3, there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, or the like, caused by the fact that the motor-driven air compressor 5 is driven in the condition that the switching device 3 is left not-closed so that the current of the motor-driven air compressor 5 flows into the current conducting device. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, so that it is possible to prevent the air-conditioning apparatus from becoming large in size. Although the switching device 3 and the power breaking device 4 are relays in the above three embodiments, they can be realized by transistors, thyristors, or the like. Although the current conducting device is a resistor, it can be realized by a transistor or the like. Various methods can be applied to other sections within the scope of the present invention. As is apparent from the above embodiment, in the electric car air-conditioning apparatus according to the present invention, in the case where current conduction continues for a period longer than a predetermined time, for example, in the case where a half-failure occurs in the motor-driven air compressor driving unit or the capacitor or the like, in the case where the capacitor is connected with its polarity reversed, or in other similar cases, the control section actuates the power breaking device to break a current from the battery. Accordingly there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, or the like, caused by over-heating of the current conducting device due to the half-failure of the motor-driven air compressor driving unit, the capacitor or the like. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, so that it is possible to prevent the air-conditioning apparatus from becoming large in size. In addition, there is no case where the capacitor is broken due to the connection of the capacitor its polarity reversed. Accordingly, there is no case where matters blown out of the broken capacitor pollute the air-conditioning apparatus to thereby deteriorate the performance and reliability. Accordingly it is possible to realize an electric car air-conditioning apparatus which is small in size, in which abnormal heating can be prevented from occurring upon occurrence of a failure, and in which damage can be prevented from occurring also when a capacitor is connected with its polarity reversed. On the other hand, even when the control section outputs a control signal to close the switching device, if a failure occurs in the switching device or in the driving circuit of the switching device, the air-conditioning motor-driven air compressor is driven by the motor-driven air compressor driving unit in the condition where the switching device is left not-closed. Therefore, when the current-conduction detecting device detects the operation of current conduction, the control section actuates the power breaking device to break a current from the battery. Accordingly, if a failure occurs in the switching device or in the driving circuit of the switching device, there occurs no deterioration of reliability, such as smoking, solder dissolving, wiring damage, or the like, caused by overheating of the current conducting device due to the fact that the motor-driven air compressor is driven in the condition that the switching device is left not-closed so that the current of the motor-driven air compressor flows into the current conducting device. It is therefore unnecessary to provide a radiator as a countermeasure to overheating, so that the air-conditioning apparatus does not become large in size. Accordingly it is possible to realize an electric car air-conditioning apparatus which is small in size, and in which abnormal heating can be prevented from occurring upon occurrence of a failure.

Claims: An electric car air-conditioning apparatus comprising: a first terminal and a second terminal to be electrically connected to a battery (2); a switching device (3) having an input terminal and an output terminal, the switching device (3) for supplying electric power from said battery (2) when the input terminal and the output terminal are shorted in accordance with a first control signal; a combined parallel-series-connection of (i) power breaking means (4) breaking its own circuit in accordance with a second control signal, (ii) a conducting device (8) having a resistance value, and (iii) said switching device (3); current-conduction detecting device (9) detecting a current flowing through said conducting device (8) to output a current-conduction detection signal; a capacitor (11) electrically connected between the output terminal of said switching device (3) and said second terminal, and a motor-driven air compressor driving unit (1) including first means (6, 7) electrically connected in parallel to said capacitor (11) to detect a voltage across said capacitor (11), said first means (6, 7) being operable to produce the first control signal causing said switching means (3) to short the input terminal and the output terminal when said detected voltage is higher than a predetermined value and to output the second control signal causing said power breaking means (4) to break its own circuit either in a case (a) where said current-conduction detection signal continues to exist for a predetermined time period while the first control signal is not being outputted, or in a case (b) where the current-conduction detection signal exists while the first control signal is being outputted, and second means (13) for driving a motor-driven air-conditioning compressor (5) by use of the electric power supplied from said battery (2) through said switching device (3). The apparatus of claim 1, wherein said combined parallel-series-connection includes a series connection of said power breaking means (4) and said conducting device (8), said series connection being electrically connected in parallel to said switching device (3), said switching device (3) having its input terminal electrically connected to said first terminal. The apparatus according to claim 1 or 2, wherein said current-conduction detecting device (9) comprises: a photo-coupler including a light emitting diode (LED) and a photo-transistor; and a resistor serially connected to said LED, a series connection of said LED and said resistor being connected in parallel to said conducting device (8).

Inventors: GOTO NAOMI, NISHIMIYA MASAFUMI, YOSHIDA MAKOTO, GOTO, NAOMI, NISHIMIYA, MASAFUMI, YOSHIDA, MAKOTO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: B60H1
IPC codes: B60H1, B60L3, H02H7, H02H9, H02J7, B60L1